Chemical Process Control

Near infrared (NIR) spectroscopy has become a critical tool for monitoring and controlling chemical processes, offering both transmissive and reflective measurement techniques. Unlike traditional Fourier Transform Infrared (FTIR) systems, which often require sample removal for off-line analysis, NIR spectroscopy operates in the fiber-optic compatible 700 nm to 2500 nm wavelength range, enabling remote, in-line monitoring. Light can be projected into a process stream using lenses or fiber optics, and the returned signal provides real-time absorption data for chemical analysis. This approach positions the spectroscopy instrumentation safely away from potentially hazardous process streams, minimizing ignition risks.

NIR spectroscopy detects absorption caused by molecular vibrations, including fundamental mid-infrared vibrations and their overtones in the short-wave infrared. Diffraction gratings separate the returned light into its constituent wavelengths, which are then captured by linear photodetector arrays such as Indium Gallium Arsenide (InGaAs) arrays from Sensors Unlimited. The resulting spectral pattern displays peaks and valleys corresponding to molecular concentrations, enabling quantitative analysis.

The high sensitivity and fast response of InGaAs detector arrays make them the industry standard for NIR applications. By providing continuous, real-time monitoring, chemical plants can achieve tighter process feedback control, reduce variability, and improve product quality. Coupled with spectral analysis software and graphs, such as those offered by StellarNet, operators gain immediate insight into process chemistry, empowering safer, more efficient, and more responsive operations.